P0656 Fuel Level Output Circuit Malfunction

P0656 code definition

The P0656 code means that the powertrain control module (PCM) has read an abnormal voltage level from the fuel level output circuit.

What the P0656 code means

The P0656 means that something in the fuel level output circuit's electrical connections or wiring, which run from the PCM to another controller interface module, is malfunctioning. The PCM gathers data from the engine in order to feed the most important information to the other electrical modules. Flawed information coming from one of the output circuits in the PCM can greatly impact the performance of the system.

What causes the P0656 code?

The most common causes for this code are:

• Defective system circuitry
• Wiring and/or electrical connectors that are corroded, broken or loose
• A defective PCM
• A fault in the low fuel level indicator bulb or fuel level sensor

What are the symptoms of the P0656 code?

The appearance of a P0656 code may come with no symptoms other than the check engine light or a non-operating low fuel indicator. Some vehicles may also experience inaccurate fuel gauges, or even inoperable gauges.

How does a mechanic diagnose the P0656 code?

To diagnose the P0656 code, the mechanic will use an OBD-II scanner. However, it is important to begin with a visual inspection of a PCM, the engine wiring harness, and all ground wires as well as electrical connectors. Replacing and repairing anything that is damaged, disconnected or loose, the mechanic will have to re-run the diagnostic to see if the code returns.

If so, look at the freeze frame data to see where the code appears in the order of codes saved because there may be other fuel level related codes that will make it easier to identify the actual cause of this code.

Common mistakes when diagnosing the P0656 code

The most common mistake made when diagnosing the P0565 code is that the engine's coolant temperature sensor is replaced prior to a more in-depth diagnostic. This allows the PCM driver to be overlooked, and it is this which is most often a cause for this code to appear.

How serious is the P0656 code?

The P0656 code does not interfere with vehicle operations, but it can cause the vehicle to display inaccurate gas levels and to persistently cause the PCM to run inefficiently due to flawed data.

What repairs can fix the P0656 code?

The P0656 is best repaired using the following processes:

• A technician should verify the code with a scanner, and begin repairing the issue by resetting the codes and doing a road test to determine if the P0656 code returns. If so, they must then move on into a more in-depth diagnosis.
• The next step is to do a visual inspection on the PCM and the wiring harnesses, ground wires, and connectors. Anything that is frayed, corroded, disconnected or damaged must be replaced and the diagnostics re-run to determine if the code will reappear.
• If the code returns, it is necessary to examine the system circuitry. This may require the use of an Autohex or Tech II scanner that looks into the CAN bus to detect the problems. Because the most common cause for this code is loose or disconnected wiring, the diagnostic CAN scanners are typically the most effective in finding the issue and making the repair.

Additional comments for consideration regarding the P0656 code

The CAN scanners can provide you with pin values and assess individual control modules without risking any electrical glitches due to flawed testing with a probe. Though individual control modules rarely fail, it is possible, and the CAN scanner may detect this, as well as the control module ground circuits.

Need help with a P0656 code?

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